Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $48.81   7.690%   $52.5635   $52.56   $52.55   $52.60  
  Purchase #2 $245.92   10.418%   $271.5399   $271.54   $271.55   $271.50  
  Purchase #3 $54.63   11.317%   $60.8125   $60.81   $60.80   $60.80  
  Purchase #4 $222.73   9.826%   $244.6154   $244.62   $244.60   $244.60  
  Purchase #5 $191.41   3.874%   $198.8252   $198.83   $198.85   $198.80  
  Purchase #6 $59.35   6.195%   $63.0267   $63.03   $63.05   $63.00  
  Purchase #7 $108.27   9.743%   $118.8187   $118.82   $118.80   $118.80  
  7 purchase totals = $931.12       $1,010.2019   $1,010.21   $1,010.20   $1,010.10